1. Field of the Invention
The present invention relates to an apparatus and method for converting scanning mode, and more particularly, to an apparatus and method for converting scanning mode which can simplify a configuration of a down-converter converting a HD or SD image of ATSC standard into an image signal of NTSC standard.
2. Description of the Related Art
In order to make it possible to process image signals generated by various scanning modes according to the development of an image signal processing technology in a conventional image signal processing apparatus such as a television, signals received in a receiving part must be processed after being converted into a form that the apparatus can process.
Thus, when processing by converting different signal modes, flickering is generated on a screen because each image signal does not correspond one to one according to the difference of processing time or processing mode.
Especially, when converting a signal of High Definition TV (HDTV) mode into a signal of NTSC format or CCIR656 format or 720*480 interlace mode corresponding to the modes, it is determined whether flickering occurs or not according as whether to use a line-memory by lines of a signal to be converted or not.
Thus, in order to remove flickering on a screen effectively, the number of line-memory installed in an apparatus for converting scanning mode of a receiving part must be increased.
But, in case of removing flickering on a screen by increasing the number of line-memory, the efficiency in a viewpoint of hardware drops remarkably.
In view of the foregoing, an object of the present invention is to provide an apparatus and method for converting scanning mode, which can remove flickering on a screen effectively with minimum number of line-memory, by enabling to process signals of many lines with one line-memory using an empty space of a line-memory effectively generated in converting a scanning mode by using a linear filter.
According to one aspect of the present invention to accomplish the object, an apparatus for converting an image signal of a progressive scanning mode to an image signal of an interlace scanning mode comprises a line-memory means to store a first line signal inputted at present among image signals of the progressive scanning mode and a converted first line signal selectively in response to a first control signal, a line-synthesis means outputting a converted first line signal by synthesizing the first line signal inputted at present and a previously inputted first line signal stored in the line-memory means in response to a first and a second synthesizing coefficient value, an output means outputting the converted first line signal in response to a second control signal and a control means controlling by providing the first and second control signal established in response to the number of lines of an image signal of the progressive scanning mode and to the number of lines of an image signal of an interlace scanning mode and the synthesizing coefficient value to the each means.
On the other hand, according to another aspect of the present invention, a method for converting scanning mode, which is for converting from a progressive scanning image having a first line number to an interlace scanning image having a second line number using one line-memory, comprises the steps of: establishing a control value to convert the first line number to the second line number; delaying a first line signal inputted at present among image signals of the progressive scanning mode for a predetermined time; selecting the delayed first line signal and a converted first line signal in response to the established control value; storing the selected first line signal in the line-memory; generating a converted first line signal by synthesizing a first line signal inputted at present among image signals of the progressive scanning mode and a previously inputted first line signal stored in the line-memory in response to the established control value; and outputting the generated first line signal selectively in response to the established control value.
Therefore, an apparatus and method for converting scanning mode according to the present invention can remove flickering on a screen effectively with minimum number of line-memory, by enabling to process signals of many lines with one line-memory using an empty space of a line-memory effectively required in converting scanning mode using a linear filter.